Wiring a Wye for DCC

Model Railroader Electronics and DCC
1

Hello All,

I’ve recently converted my pike from DC to DCC using the Bachmann EZ Command system.
It is an oval with a stub Wye on one side of the oval inwards. A simple Wye used for turning locos.
Both the turnouts from the main line and the Wye have insulated frogs; Peco #2’s Insulfrogs on the main line to an Atlas Wye.
I’ve used insulated rail joiners on all rails on both legs of the Wye just past the turnouts on the mainline.
The Wye is fed with a MRC AD520 reversing loop module drawing power from the main line, wired per the mfg. specs.
Here’s the problem:
When both sets of points are thrown to the Wye when a loco passes over the insulated rail joiners; one set of trucks on the on the mainline, on set of trucks on the Wye, a short occurs.
If I only throw the incoming set of points to the Wye, leaving the other set of points on the mainline, there are no problems. The loco then moves to the Wye, it is thrown in the other direction, the points on the mainline are reversed and away we go.
The position of the points on the Wye don’t affect operation. Once the loco is on the Wye the sequence of switching the points on the mainline doesn’t matter.
I have even been able to run one loco on the mainline loop while performing this opposed switching operation to turn another loco simultaneously!?!
This means that my switching actions need to be precise and I cannot have both sets of points from the mainline towards the Wye at the same time or the above described short occurs. Yet both sets of points can be switched to the mainline with no problems. Again, the position of the Wye switch has no effect.
I’ve communicated this to MRC with not much success.
Does anyone have any suggestions on how I can wire this Wye so that both sets of points off the main line can be thrown simultaneously rather than sequentially.

Thank you.

2

Simply stated, it should work as wired and gapped.

So, the fact that it doesn’t suggests that something is wrong with the gapping or wiring or the MRC.

We have had a few recent threads with these kinds of problems.

The quickest way to get at the heart of the problem is to eliminate the MRC unit as the culprit.

Pull out the MRC and install a DPDT toggle switch and operate the reversing section manually.

If it works that way, the MRC is defective.

If it doesn’t work that way, something is wrong with your gapping or wiring … or the turnouts themselves.

Rich

P.S. As I re-read your post, you say, “I’ve used insulated rail joiners on all rails on both legs of the Wye just past the turnouts on the mainline”.

I hope you mean that the gaps are on the divergent ends of the two mainline turnouts.

3

Thanks for your thoughts Rich,

Yes, the gaps are on the divergent ends of the two mainline turnouts—all four rails—leading to the Wye switch.

I’ll look up how to install a Dual Pole Dual Throw toggle switch and see what happens.

Any further thoughts or suggestions are welcome.

Thanks again!

4

THE SOLUTION!!!

jward, from the Bachmann Forum suggested the following:

“(T)ry putting a gap in the mainline between the two switches. the gap should be on the same rail as the frogs of the mainline switches.

(T)his is how you wire the mainline part of a wye when using all rail or power routing switches, which is what (I) suspect you have. the result(ing) short has absolutely noting to do with the autoreverse module, but is rather caused by the position of the points on the two switches setting up a short circuit on the mainline track.”

So…here’s what I did:

I gapped the frog rail between the mainline turnouts, as suggested. I also moved the pickups for the AD520 to the “outside” of the Wye on the mainline, maintaining the color coding as per the mfg. specs.

IT WORKED!!!

I can now switch both sets of points on the mainline to the Wye, run the loco to the Wye, switch the Wye to the other leg and away we go back to the mainline!!!

When the points of the Wye are switched to the mainline I have independent cab control on the Wye and the mainline.

I’ve relayed (excuse the pun) to MRC and I hope this helps anyone wishing to replicate this on their pike.

J.J.

Post Script: Thank you Rich for your trouble-shooting suggestion.
5

Do You have it wired like this with the MRC?

Click on image, for text.

Frank

6

The location of the gaps in the diagram shown in Frank’s post is correct, and your setup should have worked this way as well.

If you needed to gap the inner rail on the mainline between the two turnouts, then your turnouts must have been Electrofrogs, not Insulfrogs.

Rich

7

Hello Rich,

The turnouts are indeed insulfrog:

ST-240 No.2 Radius, R/H Turnout, Insulfrog

ST-241 No.2 Radius, L/H Turnout, Insulfrog

HO CODE 100 MARK IV WYE TURNOUT—Atlas states, “Custom-Line Turnouts have metal frogs that can be powered if necessary” However it was not modified from the stock configuration.

Being of an open mind I rewired the Wye as per Frank’s diagram. I have not ballasted my pike yet so this was not a big deal. Yes it works but I lost independent cab control on the Wye.

I then went back to the wiring that I’ve described above and was able to maintain independent cab control on both the Wye and the mainline—running two locos simultaneously. Which is what I was looking to do in the first place.

I‘d like to upload a schematic of this layout but I can’t figure out how.

Again, thank you for your troubleshooting tip and the diagram.

J.J.

8

What do you mean by “lost independent cab contro”? Autoreversers do NOT work with DC, so if you have your layout wired to use DCC or DC, you will not be able to workt he wye in DC.

Also, since the wye turnout is Atlas, it is all rails powered at all times, so you really need four total gaps, hard to tell from Frank’s picture if there are 4 gaps or just the two center rails are gapped. His picture is for a Peco Insulfrog wye which is not exactly the same electrically as Atlas. (well maybe the N scale stuff is, the HO ones are power routing whereas Atlas turnouts are not)

–Randy

9

No, the wye turnout is an Atlas…the other two are Peco insul-frog. All four ends of the turnout are gapped, per text.

Take Care! [:D]

Frank

10

Oh brother, let’s not make this thread anymore confusing than it already is.

The OP describes his setup as two Peco Insulfrogs and an Atlas wye.

Frank’s diagram shows a Peco wye. Randy is correct. But it doesn’t matter because the diagram shows all four divergent rails of the wye as gapped. You can see that as the color changes with the points movement. So, either way, Peco wye or Atlas wye, the placement of the gaps isolates the wye and creates the reversing section.

Actually, in Frank’s link, the Atlas wye is diagrammed earlier in that thread, but you cannot use that diagram because the location of the gaps don’t correspond to those on the OP’s layout.

Now, back to the OP’s issue. He has two Peco Insulfrogs (power routing) and an Atlas wye (all routes powered). He has gapped all four divergent rails on the wye. That setup should work without a short when both Peco turnouts are simultaneously thrown divergent. The wye is isolated and it becomes the reversing section.

There should not have to be a gap on the mainline where the two frog rails meet. Obviously, there is more going on with the OP’s layout than meets the eye.

Rich

11

Hello All,

Thank you all for your input.

To clarify for Randy, when I wired the Wye as per franks schematic once a loco was on the stub track and the points were thrown back to the mainline, in essence electrically cutting off the Wye, I lost the ability to control the loco on the Wye. I am running a digital system (DCC). That’s what I meant when I said I lost “independent cab control.” I apologize for the confusion.

I have a PDF schematic of how this Wye is wired now. Unfortunately I don’t know how to upload it. I go to the Insert Image and I just get two blank boxes. Any help would be greatly appreciated.

With the Wye wired as I’ve described I can now run one loco on the entire Wye; from the divergent points on the mainline turnouts, where the insulated rail joiners are, through the Wye turnout and on the stub track, back and fourth on both legs of the Wye, while simultaneously, with the points of the Wye thrown to the mainline, run another consist around the mainline loop with the stock turnouts.

If the loco on the Wye accidentally runs past the insulated rail joiners towards the mainline, when the points are not thrown in that direction, it simply stops and no short occurs. Thus avoiding a “Gomez Adams” moment on the mainline and any damage to the system.

With the points on the mainline thrown toward the Wye I can run one loco through the Wye, spot a car on the stub, pull that loco just past the Wye towards the mainline while remaining on one leg of the Wye, throw the points on the Wye in the other direction and have a second loco pick up that car from the opposite leg and return to the mainline. With quick enough fingers I can have both locos moving on the Wye simultaneously replicating prototypical spoting movements.

When moving a loco from the mainline loop to the Wye, with both sets of point thrown to the divergent track I can hear the auto reverse unit clicking and doing it’s thing so I don’t

12

J.J.,

I sent you a Private Message with my email address.

If you email me the PDF. I will post it for you.

Rich

13

Top box is the URL for the image, you need to host pictures on a photo site and link them here, you cannot upload directly to here. What goes in the box should end is a picture extenstion, like .jpg or .gif or .png.

It makes sense now, it done exactly liek Frank showed, with those Peco turnouts being power routing, it would cut power to the inside rail if the turnout on the right was thrown back to the main. Power for the AR should always come from your bus, not a set of feeders dropped to power it.

I don;t see where a gap in the top rail of the main would be needed with those facing turnouts, since they are Insulfrog versions. If they were Electrofrog - yes. I don’t know if you put a gap there - it IS mentioned in teh thread on the other forum.

–Randy

14

I am attaching two diagrams that the OP asked me to post for him.

The first diagram shows the setup, wiring and gaps, that results in a short when both turnouts are simultaneously pointed toward the wye.

The second diagram shows the setup, wiring and gaps, that the OP used to avoid a dead short when both turnouts are simultaneously pointed toward the wye.

The reason that the first diagram results in a dead short is due to the location of the wires from the input side of the auto-reverser. When the wires from the input side of the auto-reverser are placed between the two turnouts on the mainline, power routed through the auto-reverser to the reversing section (wye) is intermittent.

When the two turnouts are set to the straight through route, both mainline rails on each turnout are powered, However, when both turnouts are set to the divergent route, pointing to the wye, the frog rail of each turnout on the mainline is unpowered. That is how the power routing feature of the Peco Insufrog works. So, no power passes through the auto-reverser to the ouput side, resulting in a dead short as the loco crosses the gaps onto the wye due to mismatched polarities.

Now, if one turnout is set divergent while the other turnout remains set to the straight through route, power is still routed through the auto-reverser since both mainline rails are still powered on the turnout that is set to the straight through route. No dead short occurs as the loco crosses the gaps because the auto-reverser has power to flip and match the polarities.

Once the wires to the input side of the auto-reverser are relocated to the tail end of one of the turnouts, as in the second diagram, power to the auto-reverser is always constant, not intermittent. So, a dead short no longer occurs when both turnouts are pointed simultaneously to the wye.

As far as placing a gap between the two mainline frog rails between the turnouts, it is not necessary. &nb

15

Hello Rich,

As per your explanation I have removed the insulated rail joiner from the frog side of the mainline between the turnouts and replaced it with a metal rail joiner keeping the wiring the same.

IT WORKS!!! It does exactly what I wanted it to when I began this addition to my pike!

I just ran a consist around the mainline loop while simultaneously spotting a car on the stub with two switchers moving along each leg of the Wye with the points on the mainline. All three had independent cab control throughout. I was also able to switch both points to the Wye and perform the same spotting manuver from the mainline to the stub.

Thank you all who have helped solve this problem with your input and knowledge. I hope this will help the next modeler wishing to repeat this on their pike.

Now on to the snowplow project.

Thank you all again.

16

J.J.

Thanks for your follow up.

As you say, these threads help not only the OP but also other interested reads who follow these threads for help and advice.

This was a case of “a picture speaks a thousand words”.

Seeing the placement of the wires for the input side of the auto-reverser between the two turnouts was all that was needed to visualize the problem with the dead short.

Great follow through on your part.

Rich